Insights from the CLEARING HOUSE Co-Design Workshop in Gelsenkirchen by Ian Whitehead, European Forest Institute (EFI)

On 15-16 September 2023, I joined and contributed to the third and final CLEARING HOUSE (CH) co-design workshop, which took place in the case study City of Gelsenkirchen. During two days of intense activity, participants from diverse local organisations – including local government, the NRW State Forestry service (NRW Wald und Holz), NGOs and local citizens’ groups – were able to learn about the outcomes of the CH Project. We also participated in lively discussions on creating a sustainable future for Gelsenkirchen, whilst enjoying convivial company and some tasty, locally produced food. Fortunately, the weather was kind to us as well, with beautiful autumn sunshine blessing both days.

The CLEARING HOUSE Project was launched back in 2019 with the ambitious goal to analyse and develop the potential of Urban Forestry Nature Based Solutions (NBS) across China and Europe. The overall aim of the Project is to foster the resilience of cities which are facing major ecological, socio-economic and human wellbeing challenges. Gelsenkirchen is one of five European case studies cities, with a further five cities in China.


In recent years, the City of Gelsenkirchen has become renowned for its innovative approach to post- industrial greening and the reclamation and conversion of former brownfield sites to create new spaces for people and biodiversity. This has been primarily down to the inspirational lead of the City’s forward-looking administration and its participation in “bigger picture” regional development initiatives, such as the famous Emscher Landschaftspark and the Regionalverband Ruhr (RVR).

During two days of the Co-design Workshop, participants had the chance to visit a couple of wonderful examples of former industrial sites which have been transformed to create attractive, rich and accessible greenspaces: the Industriewald at Rheinelbepark and the Grünlabor Hugo.

Exploring the Project’s Achivements and Collaborative Learning on Day One

The first day of the Workshop on Friday 15th September was dedicated to knowledge exchange between people with a professional involvement and interest in urban forestry. I presented some results from the CH project, whilstmy EFI colleague Gesche Schifferdecker moderated the event on the first day. I outlined details of the Project Work Packages relevant to Gelsenkirchen and the Deliverables, or outputs, associated with these. This included an update on progress so far achieved in terms of implementation and some information about future outputs/deliverables which were still in the pipeline.


As I explained (in my finest German !), the outputs of the Project are diverse in character, as are their intended target audiences. In this respect, deliverables linked directly to collaborative learning processes (the overall theme of Work Package 3) are most likely to be of interest and relevance to local stakeholder groups. By contrast some other outputs provide more of a strategic overview and will consequently be mainly useful to university researchers and academics.

The Co-design Workshops are one of the key collaborative learning outputs of CLEARING HOUSE. Two earlier workshops took place in 2020 and 2021. The aim of these workshops has been to bring together diverse stakeholders from government, NGOs, businesses and the local community for a creative exchange of information, ideas and inspiration on all topics related to Urban Forestry and Nature Based Solutions.

Citizen Science and Technology in Urban Forestry

Another aspect of collaborative learning is through the use of citizen science based approaches which give local citizens the chance to become actively engaged in scientific data collection. One popular aspect of this has been the development of a Marteloscope, which is located in an area of mature broadleaved forest close to the Rheinelbepark. The Marteloscope was inaugurated during the first day of the workshop with the enthusiastic participation of local stakeholders and attendance from the media.  (for more info see: The city of contrasts: Learning about forests and trees in Industriewald and Rheinelbepark in Gelsenkirchen – Resilience Blog (

For the uninitiated, a Marteloscope is a permanent research plot within the forest in which tree measurements and associated software are linked to provide a framework for in-forest training in selection and marking. Marteloscopes were first developed in France and the name derives from the French word “martelage”, which means tree selection and the Greek word “skopein”, meaning to watch. It consists of a 1 hectare rectangular plot divided in 16 subplots of 25×25 m (numbered from 1 to 16) in which, at least, the species, height and diameter at breast height of every tree are measured and recorded. Based on these measures, its basal area and volume are calculated. For more information check out:

The workshops also covered other diverse aspects of citizen science, including a Participatory GIS  mapping study which has been coordinated by researchers from the Humboldt University in Berlin. The study enables citizens to record their positive and negative impressions of time spent in the greenspaces of Gelsenkirchen, to rate their experiences and to provide critical feedback to better inform management decision making processes. This information is recorded using a simple app which can be downloaded to any Smartphone, thereby helping ease of data collection and the removal of some traditional barriers to participation.

On a similar tech theme, there was also a presentation on software that can be used to model environmental processes called Über Uns – TransparenTree. It was developed to help determining future tree planting priorities through investigating the age structure of the tree population, the species involved, spatial distribution patterns and health issues, including susceptibility to insect pests and pathogens. Through such data, foresters can propose better informed management, planting and maintenance regimes.

We also discussed whether some outputs of the project were considered to be overly scientific for the consumption by local stakeholders. Certainly, there is a perceived need for more targeted dissemination material which can easily communicate results to more generalist audiences, through use of simple and non-scientific language. It would also be beneficial to translate some of the general communication materials into local languages (including German), such as the excellent CH “City of Trees” Educational Package. This would be a good starting point to tailor the project outputs, to the needs of local stakeholders, who often encounter problems with more technical language.

Envisioning Gelsenkirchen’s Green and Sustainable Future on Day Two

On Saturday 16th the City of Gelsenkirchen and the urban forest managers invited interested local citizens to the “Grünlabor Hugo”, a former colliery site which has now been transformed into a multifunctional greenspace. The site features diverse habitats and functions, including woodlands, energy coppice plantations, extensive recreational path networks and community growing spaces for residents.

The Saturday session also featured a rerun of some presentations from the previous day, which were held in the NRW Regional Forest Office. Following on from this, there was the chance for an “al fresco” healthy lunch in the attractive surroundings of the Grünlabor Hugo.

The lunch was hosted by some enthusiastic members of the Grünlabor Hugo Community Gardening Group. They treated everyone to some tasty locally grown produce, including honey produced on site and freshly pressed apples from nearby gardens and orchards. The convivial surroundings also provided a great opportunity for some informal networking and discussions.

These informal dialogues were taken up later on through a more structured and interactive “World Café” session. Participants sat in a circle and exchanged views and ideas on the future of urban forestry, NBS and wider sustainability issues affecting Gelsenkirchen. In particular, participants were asked to think ahead and imagine how Gelsenkirchen might look in the year 2040 and what innovative solutions might be required to create a green and sustainable city of the future. The presentations and engaging exchanges were recorded by a graphic artist who prepared an attractive and detailed pictorial map of the resulting discussions.

Overall, the dialogue was constructive and inclusive, with everyone present having the opportunity to contribute and to have their say in an open and non-judgemental atmosphere. Exchanges were broad ranging and stressed the need for integrated approaches to urban greening and sustainability initiatives, going well beyond the usual domain of urban forestry and NBS. Diverse, but interrelated themes included: increasing street tree provision, reducing car dependency, climate change mitigation, greening school grounds, creating green roofs and facades, developing local food production, participation of young people, social integration, education and skills training.

Certainly, there appears to be an emerging view that urban forestry and Nature Based Solutions should be part of a bigger overall package of measures aimed at creating more sustainable, inclusive and attractive cities.


Finally, although CLEARING HOUSE is coming to an end, it was stressed that this should only be the start of the City’s involvement in urban forestry NBS and that there would be further opportunities for collaboration in future, both at a local and on an international scale. Amongst the initiatives mentioned were the Uforest Alliance and the European Forum on Urban Forestry. The development of coordinated approaches through development of Urban Greening Plans could also provide opportunities for creating future synergies.

Overall, an inspiring and thought-provoking couple of days. We thank the people of Gelsenkirchen for all their great work in organising and hosting the 2-day Workshop.